Topography based patterning

ABSTRACT

A mask having features formed by self-organizing material, such as diblock copolymers, is formed on a partially fabricated integrated circuit. Initially, a copolymer template, or seed layer, is formed on the surface of the partially fabricated integrated circuit. To form the seed layer, diblock copolymers, composed of two immiscible blocks, are deposited in the space between copolymer alignment guides. The copolymers are made to self-organize, with the guides guiding the self-organization and with each block aggregating with other blocks of the same type, thereby forming the seed layer. Next, additional, supplemental diblock copolymers are deposited over the seed layer. The copolymers in the seed layer guide self-organization of the supplemental copolymers, thereby vertically extending the pattern formed by the copolymers in the seed layer. Block species are subsequently selectively removed to form a pattern of voids defined by the remaining block species, which form a mask that can be used to pattern an underlying substrate. The supplemental copolymers augment the height of the copolymers in the seed layer, thereby facilitating the use of the copolymers for patterning the underlying substrate.

PRIORITY CLAIM

This application is a divisional of U.S. patent application Ser. No.11/445,907, filed Jun. 2, 2006.

REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.11/389,581 to Gurtej Sandhu, filed Mar. 23, 2006, entitled TopographyDirected Patterning, the entire disclosure of which is incorporated byreference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to integrated circuit fabrication and,more particularly, to printing techniques.

2. Description of the Related Art

As a consequence of many factors, including demand for increasedportability, computing power, memory capacity and energy efficiency,integrated circuits are continuously being made more dense. The sizes ofthe constituent features, e.g., electrical devices and interconnectlines, that form the integrated circuits are constantly being decreasedto facilitate this scaling.

The trend of decreasing feature size is evident, for example, in memorycircuits or devices such as dynamic random access memories (DRAMs),flash memory, static random access memories (SRAMs), ferroelectric (FE)memories, etc. To take one example, DRAM typically comprises millions ofidentical circuit elements, known as memory cells. In general, acapacitor-based memory cell, such as in conventional DRAM, typicallyincludes two electrical devices: a storage capacitor and an access fieldeffect transistor. Each memory cell is an addressable location that canstore one bit (binary digit) of data. A bit can be written to a cellthrough the transistor and can be read by sensing charge in thecapacitor. Some memory technologies employ elements that can act as botha storage device and a switch (e.g., dendritic memory employingsilver-doped chalcogenide glass) and some nonvolatile memories do notrequire switches for each cell (e.g., magnetoresistive RAM) orincorporate switches into the memory element (e.g., EEPROM for flashmemory). By decreasing the sizes of the electrical devices thatconstitute a memory cell and the sizes of the conducting lines thataccess the memory cells, the memory devices can be made smaller.Additionally, storage capacities can be increased by fitting more memorycells on a given area in the memory devices. The need for reductions infeature sizes, however, is more generally applicable to integratedcircuits, including general purpose and specialty processors.

The continual reduction in feature sizes places ever greater demands onthe techniques used to form the features. For example, photolithographyis commonly used to pattern these features. Typically, photolithographyinvolves passing light through a reticle and focusing the light onto aphotochemically-active photoresist material. Just as a slide has animage to be projected onto a screen, the reticle typically has a patternto be transferred to a substrate. By directing light or radiationthrough the reticle, the pattern in the reticle can be focused on thephotoresist. The light or radiation causes a chemical change in theilluminated parts of the photoresist, which allows those parts to beselectively retained or removed, depending on whether positive ornegative photoresist is used, relative to parts which were in theshadows. Thus, the exposed and unexposed parts form a pattern in thephotoresist. It will be appreciated that this pattern can be used as amask to form various features of an integrated circuit, includingconductive lines or parts of electrical devices.

Because lithography is typically accomplished by projecting light orradiation onto a surface, the ultimate resolution of a particularlithography technique depends upon factors such as optics and light orradiation wavelength. For example, the ability to focus well-definedpatterns onto resist depends upon the size of the features and on thewavelength of the radiation projected through the reticle. It will beappreciated that resolution decreases with increasing wavelength, due,among other things, to diffraction. Thus, shorter wavelength radiationis typically required to form well-resolved features, as the sizes ofthe features decrease. Consequently, to facilitate reductions in featuresizes, lower and lower wavelength systems have been proposed.

For example, 365 nm, 248 nm, 193 nm and 157 nm wavelength systems havebeen developed as features sizes have decreased. Additional reductionsin feature sizes, e.g., down to 20 nm features, may require even shorterwavelength systems. For example, X-ray based lithography, using X-rayradiation instead of light, has been proposed to form very smallfeatures, such as 20 nm features. Another proposed technology is extremeultraviolet (EUV) lithography, using, e.g., 13.7 nm radiation. X-ray andEUV lithography, however, are expected to be prohibitively expensive toimplement. In addition to cost, the techniques face various technicalobstacles. For example, for X-ray lithography, these obstacles includedifficulties in forming high quality reticles which are sufficientlyopaque to X-rays and difficulties in devising resists which aresufficiently sensitive to the X-rays. Moreover, rather than using opticsto focus radiation on the resist, some X-ray systems place the reticleclose to the resist, to directly expose the resist to X-rays passingthrough the reticle. This can cause complications in aligning thereticle with the resist and, in addition, places significant demands onthe flatness of both the reticle and the resist. In addition, X-raylithography can use reflective as opposed to refractive optics, whichcan require a complete redesign of optical elements and related systems.Similarly, other high resolution lithography techniques, including ionbeam and electron beam lithography, have their own technical andpractical obstacles, including high complexity and costs.

Accordingly, there is a continuing need for high resolution methods topattern small features on semiconductor substrates.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the Detailed Description ofthe Preferred Embodiments and from the appended drawings, which aremeant to illustrate and not to limit the invention, and wherein:

FIG. 1 is a schematic cross-sectional side view of a partially formedintegrated circuit, in accordance with preferred embodiments of theinvention;

FIG. 2 is a schematic cross-sectional side view of the partially formedintegrated circuit of FIG. 1 after forming features in a photoresistlayer, in accordance with preferred embodiments of the invention;

FIG. 3 is a schematic cross-sectional side view of the partially formedintegrated circuit of FIG. 2 after etching through a hard mask layer, inaccordance with preferred embodiments of the invention;

FIG. 4 is a schematic cross-sectional side view of the partially formedintegrated circuit of FIG. 3 after removing the photoresist layer, inaccordance with preferred embodiments of the invention;

FIG. 5 is a schematic, cross-sectional side view of the partially formedintegrated circuit of FIG. 4 after widening spaces between lines in thehard mask layer, in accordance with preferred embodiments of theinvention;

FIG. 6 is a schematic, cross-sectional side view of the partially formedintegrated circuit of FIG. 5 after depositing a layer of a blockcopolymer solution, in accordance with preferred embodiments of theinvention;

FIG. 7 is a schematic, cross-sectional side view of the partially formedintegrated circuit of FIG. 6 after self-organization of the blockcopolymers to form a copolymer template or seed layer, in accordancewith preferred embodiments of the invention;

FIGS. 8 and 9 are schematic, top plan views of the partially formedintegrated circuit of FIG. 7 showing exemplary possible copolymerarrangements resulting from the self-organization of the blockcopolymers, in accordance with preferred embodiments of the invention;

FIG. 10 is a schematic, cross-sectional side view of the partiallyformed integrated circuit of FIG. 7 after depositing an additional layerof block copolymers, in accordance with preferred embodiments of theinvention;

FIG. 11 is a schematic, cross-sectional side view of the partiallyformed integrated circuit of FIG. 10 after self-organization of theblock copolymers in the additional layer of block copolymers, inaccordance with preferred embodiments of the invention;

FIG. 12 is a schematic, cross-sectional side view of the partiallyformed integrated circuit of FIG. 11 after selectively removing a blockcopolymer species in the additional layer of block copolymers and in thecopolymer template, in accordance with preferred embodiments of theinvention;

FIG. 13 is a schematic, cross-sectional side view of the partiallyformed integrated circuit of FIG. 12 after transferring the patterndefined by the block copolymers into the underlying substrate, inaccordance with preferred embodiments of the invention;

FIG. 14 is a schematic, cross-sectional side view of the partiallyformed integrated circuit of FIG. 13 after stripping the blockcopolymers, in accordance with preferred embodiments of the invention;and

FIGS. 15 and 16 are schematic, perspective views of the partially formedintegrated circuit of FIG. 14 showing exemplary patterns formed in thesubstrate, in accordance with preferred embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The ability of block copolymers to self-organize can be used to formmask patterns. Block copolymers are formed of two or more chemicallydistinct blocks. For example, each block can be formed of a differentmonomer. The blocks are preferably immiscible or thermodynamicallyincompatible, e.g., one block can be polar and the other can benon-polar. Due to thermodynamic effects, the copolymers willself-organize in solution to minimize the energy of the system as awhole; typically, this causes the copolymers to move relative to oneanother, e.g., so that like blocks aggregate together, thereby formingalternating regions containing each block type or species. For example,if the copolymers are formed of polar and non-polar blocks, the blockswill segregate so that non-polar blocks aggregate with other non-polarblocks and polar blocks aggregate with other polar blocks. It will beappreciated that the block copolymers may be described as aself-organizing material since the blocks can move to form a patternwithout application of an external force to direct the movement ofparticular individual molecules, although heat may be applied toincrease the rate of movement of the population of molecules as a whole.

In addition to interactions between the block species, theself-organization of block copolymers can be influenced by topographicalfeatures, such as steps on the surface on which the block copolymers aredeposited. For example, a diblock copolymer, a copolymer formed of twodifferent block species, can form alternating regions which are eachformed of a substantially different block species. Whenself-organization of block species occurs in the area between the wallsof a step, the steps can interact with the blocks such that, e.g., eachof the alternating regions formed by the blocks can be made to form aregular pattern with features oriented parallel to the walls. Inaddition, the self-organization of block copolymers can be guided byphotolithographically modifying a surface, without forming steps in thesurface, as disclosed in: Stoykovich et al., Science 308, 1442 (2005);Kim et al., Nature 424, 411 (2003); and Edwards et al., Adv. Mater. 16,1315 (2004). The entire disclosure of each to these references isincorporated by reference herein.

Such self-organization can be useful in forming masks for patterningfeatures during semiconductor fabrication processes. For example, one ofthe alternating regions can be removed, thereby leaving the materialforming the other region to function as a mask. The mask can be used topattern features such as electrical devices in an underlyingsemiconductor substrate. An exemplary process for forming a copolymermask is disclosed in U.S. patent application Ser. No. 11/389,581 toGurtej Sandhu, filed Mar. 23, 2006, entitled TOPOGRAPHY DIRECTEDPATTERNING, the entire disclosure of which is incorporated by referenceherein.

It will be appreciated that the thickness of a copolymer film caninfluence the self-organization of the copolymers and the pattern formedby the copolymers. Thus, depending on the desired pattern, the copolymerfilm can thin, leading to the formation of a thin mask. Becauseprocessing through the mask, e.g., etching an underlying substratethrough the mask, can cause some wearing away of the mask, the mask maybe too thin for some applications. For example, if an etch chemistry hasinsufficient selectivity for the substrate, the mask may be undesirablyworn away before a pattern transfer to the substrate is complete.

In preferred embodiments of the invention, the height of theself-organized copolymers is augmented to increase the thickness of themask formed by the copolymers. Guide features are patterned and trimmedover a substrate to achieve a desired spacing between the guidefeatures. A film of copolymers is deposited and the copolymers are madeto self-organize between guide features to form an initial mask layerhaving alternating domains, with each domain formed substantially oflike block species. For example, the domains can be lines, with linesformed substantially of polar block species alternating with linesformed substantially of non-polar block species.

The height of the initial mask layer is then preferably augmented usinga self-organizing material, preferably additional, supplemental blockcopolymers, deposited over the initial mask layer. It will beappreciated that the organized copolymers of the initial mask layerallow the initial mask layer to act as a copolymer template or seedlayer, which guides the supplemental copolymers to form a desiredpattern. Preferably, particular block species of the supplementalcopolymers preferentially align with particular block species in thecopolymer template, effectively vertically extending the block domainsin the copolymer template. In some embodiments, the supplementalcopolymers and the template copolymers are the same, so that like blockspecies aggregate together. Some of the blocks from both the templateand the supplemental copolymer layer are subsequently selectivelyremoved. The remaining block species can be used as a mask forpatterning of underlying materials, e.g., during the fabrication ofintegrated circuits.

Advantageously, the preferred embodiments allow the formation of small,closely-spaced step features which might otherwise need to be formedusing newer, relatively complex and expensive lithography techniques.Conventional, proven and relatively inexpensive lithography techniquescan be utilized to form guides for directing the self-organization ofblock copolymers. Moreover, the self-organizing behavior of blockcopolymers allows the reliable formation of very small features, therebyfacilitating the formation of a mask with a very small feature size. Forexample, features having a critical dimension of about 1 nm to about 100nm, more preferably, about 2 nm to about 50 nm and, more preferably,about 3 nm to about 30 can be formed.

In addition, augmentation of the mask features advantageously allows themasks to be used in applications where a single self-organized copolymermask is too thin for effective processing. For example, the augmentedmask can be used in applications where the substrate is difficult toetch, requiring a long or aggressive etch (e.g., when etching multipledisparate substrate materials), or where etch chemistries still remove asignificant amount of copolymer material due to low etch selectivity forsubstrate material. Moreover, higher quality patterns are possible,since the augmentation minimizes the need to form a thick initialcopolymer mask, thereby allowing the formation of the template mask tobe optimized for forming well-defined features, rather than optimizingfor thicknesses sufficient to directly pattern a substrate.

Reference will now be made to the Figures, wherein like numerals referto like parts throughout. It will be appreciated that the Figures arenot necessarily drawn to scale.

In a first phase of methods according to the preferred embodiments, acopolymer template or seed layer is formed. With reference to FIG. 1, across-sectional side view of a partially formed integrated circuit 100is illustrated. Masking layers 120, 130 are preferably provided above asubstrate 110 to form guides for copolymer alignment. The materials forthe layers 120, 130 overlying the substrate 110 are preferably chosenbased upon consideration of the interaction of the layers with blockcopolymer materials to be used and of the chemistry and processconditions for the various pattern forming and pattern transferringsteps discussed herein. For example, because patterns in upper layersare preferably transferred to lower layers, the lower masking layer 130is preferably chosen so that it can be selectively etched relative toother exposed materials. It will be appreciated that a material isconsidered selectively, or preferentially, etched when the etch rate forthat material is at least about 2-3 times greater, preferably at leastabout 10 times greater, more preferably at least about 20 times greaterand, most preferably, at least about 50 times greater than that forsurrounding materials. Because an objective for the masks formed hereinis to allow well-defined patterns to be formed in the substrate 110, itwill be appreciated that one or more of the layers 120, 130 can beomitted or substituted, or additional layers can be added, if suitableother materials, chemistries and/or process conditions are used forpattern forming and transfer.

It will be appreciated that the “substrate” to which patterns aretransferred can include a single material, a plurality of layers ofdifferent materials, a layer or layers having regions of differentmaterials or different structures in them, etc. These materials caninclude semiconductors, insulators, conductors, or combinations thereof.For example, the substrate can comprise doped polysilicon, a singlecrystal electrical device active area, a silicide, or a metal layer,such as a tungsten, aluminum or copper layer, or combinations thereof.In some embodiments, the mask features discussed below can directlycorrespond to the desired placement of conductive features, such asinterconnects, in the substrate. In other embodiments, the substrate canbe an insulator and the location of mask features can correspond to thedesired location of insulation between conductive features, such as indamascene metallization. The mask features can be used as a hard mask todirectly etch the substrate, or can be used to transfer a pattern toanother underlying layer, e.g., a carbon, preferably transparent carbon,layer, which is then used to transfer the pattern to one or moreunderlying layers, such as the substrate.

With continued reference to FIG. 1, the selectively definable layer 120overlies a hard mask, or etch stop, layer 130, which overlies thesubstrate 110. The selectively definable layer 120 is preferablyphotodefinable, e.g., formed of a photoresist, including any photoresistknown in the art. For example, the photoresist can be any photoresistcompatible with extreme ultraviolet systems (e.g., 13.7 nm wavelengthsystems), 157 nm, 193 nm, 248 nm or 365 nm wavelength systems, or 193 nmwavelength immersion systems. Examples of preferred photoresistmaterials include argon fluoride (ArF) sensitive photoresist, i.e.,photoresist suitable for use with an ArF light source, and kryptonfluoride (KrF) sensitive photoresist, i.e., photoresist suitable for usewith a KrF light source. ArF photoresists are preferably used withphotolithography systems utilizing relatively short wavelength light,e.g., 193 nm. KrF photoresists are preferably used with longerwavelength photolithography systems, such as 248 nm systems. Inaddition, while the preferred embodiments can obviate the need to defineextremely small features with expensive, relatively new direct formationtechniques such as extreme ultraviolet systems (including 13.7 nmwavelength systems) or electron beam lithographic systems, such systemscan also be used, if desired. In addition, maskless lithography, ormaskless photolithography, can be used to define the selectivelydefinable layer 120. In other embodiments, the layer 120 and anysubsequent resist layers can be formed of a resist that can be patternedby nano-imprint lithography, e.g., by using a mold or mechanical forceto form a pattern in the resist.

The material for the hard mask layer 130 preferably comprises aninorganic material, which is not a polymer. Exemplary materials includesilicon oxide (SiO₂), silicon or a dielectric anti-reflective coating(DARC), such as a silicon-rich silicon oxynitride. The hard mask layer130 comprises silicon oxide in the illustrated embodiment.

With reference to FIG. 2, the photodefinable layer 120 is exposed toradiation through a reticle and then developed to leave a patterncomprising features 122 which are formed of photodefinable material. Itwill be appreciated that the pitch of the resulting features 122, e.g.,lines, is equal to the sum of the width of a line 122 and the width of aneighboring space 124. The pitch of the features 122 can be, e.g., about400 nm or less, preferably, about 300 nm or less, more preferably, about200 nm or less or about 100 or less. In an exemplary embodiment, thefeatures 122 can have a critical dimension of about 140 nm and a pitchof about 280 nm.

With reference to FIG. 3, the pattern in the photodefinable layer 120 istransferred to the hard mask layer 130, thereby forming hard maskfeatures 132 in the hard mask layer 130. The pattern transfer ispreferably accomplished using an anisotropic etch, such as an etch usinga fluorocarbon plasma, although a wet (isotropic) etch may also besuitable if the hard mask layer 130 is sufficiently thin. Exemplaryfluorocarbon plasma etch chemistries include CFH₃, CF₂H₂, CF₃H andCF₄/HBr. With reference to FIG. 4, resist forming the photodefinablelayer 120 is also preferably removed, e.g., by plasma ashing.

With reference to FIG. 5, the hard mask features 132 (FIG. 4) aretrimmed to form guides 134 for copolymer alignment. The hard maskfeatures 132 can be trimmed using a wet or dry etch. The trimadvantageously allows the formation of features having smaller criticaldimensions than could easily be formed using conventionalphotolithography. For example, hard mask features 132 having a criticaldimension of about 140 nm and a pitch of about 280 nm can be trimmed toform guides 134 having a critical dimension of about 35 nm and the samepitch of about 280 nm. In other embodiments, the photoresist features122 (FIG. 2) can be trimmed in addition to, or instead of, the hard maskfeatures 132, thereby allowing guides 134 of the desired size to beformed without the need to trim the hard mask features 132.

Block copolymers are next applied and block copolymer self-organizationis facilitated to form a mask pattern over the substrate 110. A suitablemethod for forming self-organized block copolymer patterns is disclosedin Block, IEE Transactions in Nanotechnology, Vol. 3, No. 3, September2004. The entire disclosure of that reference is incorporated byreference herein.

With reference to FIG. 6, a film 160 of block copolymer material isdeposited between and over the guides 134. The copolymer comprisesblocks of polymer material which can be selectively etched relative toone another and which can self-organize in a desired and predictablemanner, e.g., the blocks are preferably immiscible and will segregateunder appropriate conditions to form domains predominantly containing asingle block species. In the exemplary illustrated embodiment, thecopolymer is a diblock copolymer, comprising, e.g., polystyrene (PS) andpoly-methylmethacrylate (PMMA) in a 70:30 PS:PMMA ratio with a totalmolecular weight of 64 kg/mol. The diblock copolymers can be provideddissolved in a solvent, e.g., toluene. Preferably, each of thecopolymers are substantially the same size and composition, to increasethe predictability and regularity of the patterns formed by theself-organization of the copolymers. It will be appreciated that thetotal size of each diblock copolymer and the ratio of the constituentblocks and monomers are preferably chosen to facilitateself-organization and to form organized block domains having desireddimensions. For example, it will be appreciated that a block copolymerhas an intrinsic polymer length scale, the average end-to-end length ofthe copolymer in film, including any coiling or kinking, which governsthe size of the block domains. A copolymer solution having longercopolymers may be used to form larger domains and a copolymer solutionhaving shorter copolymers may be used to form smaller domains. The blockcopolymers can be deposited by various methods, including, e.g., spin-oncoating, spin casting, brush coating or vapor deposition.

The thickness of the copolymer film 160 can be chosen based upon thedesired pattern to be formed by the copolymers. It will be appreciatedthat, up to a particular thickness related to the polymer length scaleand the environment in which the polymers are disposed, e.g., thedistance between and the height of the guides 134, the copolymers willtypically orient to form alternating, substantially lamellar domainsthat form parallel lines, as viewed in a top-down view (FIG. 8). Suchlamellae can be used to pattern, e.g., interconnects, or the lateralextension of the lamellae can be limited to form isolated features,e.g., transistor gates. Above a particular thickness related to thepolymer length scale and the environment in which the polymers aredisposed, the copolymers will typically orient to formvertically-extending pillars, such as cylinders, or spheres (FIG. 9).The cylinders can advantageously be used to pattern isolated features,e.g., vias or transistor gates. Thus, the pattern to be formed canadvantageously be selected by appropriate selection of copolymer filmthickness. Alternatively, other variables, such as copolymer compositionor process conditions can be modified to facilitate the formation ofvertically extending pillars or horizontally extending lamellae for agiven thickness through appropriate selection of interfacialinteractions between the blocks of the copolymer as well as thesubstrate surfaces.

For forming lamellae, the copolymer film thickness is preferably lessthan about the length scale of the copolymers forming the film. Forexample, where the copolymer length scale is about 35 nm, the thicknessof the films is preferably about 35 nm or less, more preferably, about30 nm or less and, most preferably, about 25 nm or less. In oneembodiment, the thickness is about 20 nm.

It will be appreciated that the thickness of the film 160 can be greaterthan, equal to or less than the height of the guides 134. As illustratedand discussed further below, a thickness which is greater than theheight of the guides 134 can have advantages for providing a copolymerreservoir. In other embodiments, a thickness which is equal to or, morepreferably, less than the height of the guides 134 can be advantageousby forming isolated islands of copolymers between the guides 134,thereby preventing cross-diffusion of copolymers between the islands.

While the invention is not bound by theory, it will be appreciated thatthe different block species can self-aggregate due to thermodynamicconsiderations in a process similar to the phase separation ofmaterials. The self-organization is guided by the guides 134, whichencourage the constituent blocks of the block copolymers to orientthemselves along the length of the guides 134 due to interfacialinteractions. It will be appreciated that the self-organization canresult in a more efficient packing of the copolymer species. As aresult, in some cases, the free copolymers available for theself-organization can be depleted if the copolymer film 160 extends overtoo large of an expanse, causing an area in the middle of the expanse tobe formed without organized copolymers. Thus, in some embodiments, thecopolymer film 160 is preferably sufficient thick to extend above theguides 134 to provide a reservoir of copolymers for theself-organization which occurs between the guides 134. In addition, thedistance between the guides 134 can be chosen to be sufficiently smallto minimize the depletion effect that can occur over large expanses.

With reference to FIG. 7, the block copolymers in the copolymer film 160are allowed to self-organize. The self-organization can be facilitatedand accelerated by annealing the partially-fabricated integrated circuit100. The temperature of the anneal is preferably chosen to besufficiently low to prevent adversely affecting the block copolymers orthe partially-fabricated integrated circuit 100. In the illustratedembodiment, the anneal is preferably performed at a temperature of lessthan about 250° C., more preferably, less than about 200° C. and, mostpreferably, about 180° C. Advantageously, the anneal can also causecross-linking of the copolymers, thereby stabilizing the copolymers forlater etching and pattern transfer steps.

The pattern of lamellae resulting after the anneal is shown in FIG. 7.Domains 162 of one block species, e.g., PS, and domains 164 of the otherblock species, e.g., PMMA, alternate between the guides 134. It will beappreciated that the sizes of the block domains are determined by thesizes of the block species forming them. Thus, a seed layer or copolymertemplate 170 is formed.

With reference to FIG. 8, a top-down view of the partially fabricatedintegrated circuit of FIG. 7 is shown. The PS domains 162 can be seenalternating with the PMMA domains 164. Both domains 162 and 164 extendalong the length of the guides 134.

With reference to FIG. 9, in other embodiments, the thickness of thecopolymer film 160 (FIG. 6) is chosen so as to form vertically extendingcylinders (or other isolated pillar shapes, including pillars havingrectangular or cubic horizontal cross-sectional areas) comprising PS andPMMA, and the guides 134 are preferably chosen with a height sufficientto guide the copolymer blocks such that rows of the cylinders align in adesired direction. The resulting arrangement, from a top-down view, hasregions 162 a of PS surrounded by regions 164 a of PMMA. Such anarrangement can be useful for forming, e.g., contact vias. In addition,the pillars can advantageously be applied in some arrangements forpatterning arrays of features, particularly dense arrays of features,such as capacitors for memory applications, including DRAM. In sucharrangements, the pillars can have a cylindrical, a rectangular or cubichorizontal cross-sectional area, with the rectangular or cubic pillarshaving advantages in some applications by providing a higher surfacearea structure.

With reference to FIG. 10, a supplemental layer 180 of self-organizingmaterial is deposited over the seed layer 170 to vertically extend thepattern in the seed layer 170. The self-organizing material forming thesupplement layer 180 is preferably a copolymer, more preferably a blockcopolymer. The material forming the supplemental layer 180 is chosen tointeract with the seed layer 170 such that the domains 162, 164 and theguides 134 of the seed layer 170 are able to direct the organization ofchemical species forming the material. For example, where the seed layer170 includes polar and non-polar block species, the layer can also havepolar and non-polar block species. In some embodiments, supplementalblock copolymers forming the layer 180 are the same as the blockcopolymers of the film 160 (FIG. 6), although in other embodiments theblock copolymers can be different but have chemical moieties which allowthem to interact predictably with one another. Where the block speciesare the same, the supplemental copolymers can have the same length ordifferent lengths from the copolymers of the film 160, although thelengths and the concentration or volume fraction of the supplementalcopolymers in the supplemental layer 180 are preferably chosen tofacilitate extending the pattern of the seed layer 170 into thesupplemental layer 180. In addition, it will be appreciated that thesupplemental layer 180 is preferably deposited to a height sufficient toform a copolymer mask with a desired height for etching underlyingmaterials. The supplemental layer 180 can have a thickness greater thanthe intrinsic length scale of the copolymers forming it. Preferably, thesupplemental layer 180 can have a height of about 10 nm to about 50 nmand, more preferably, about 10 nm to about 200 nm.

With reference to FIG. 11, interactions between the supplementalcopolymers of the supplemental layer 180 and the domains 162, 164 andthe guides 134 cause the supplemental copolymers to organize intodomains 182, 184. In some embodiments, this self-organization can beaccelerated by subjecting the supplemental layer 180 to an anneal suchas that discussed above for the film 160 (FIG. 6). The anneal canadvantageously cause cross-linking of the copolymers, thereby helping tostabilize the copolymer blocks, especially during later selective blockremoval steps.

With continued reference to FIG. 11, the domains 182, 184 advantageouslyalign to form the same pattern as the domains 162, 164, as viewed from atop down view. Thus, the pattern formed by the domains 162, 164 may besaid to be transferred to the supplemental layer 180 and effectivelyvertically extending the domains 162, 164. Preferably, the domains 162,164 are organized in a substantially regular pattern and the domains182, 184 are also organized in a substantially regular pattern.

Advantageously, the supplemental copolymers can repair defects in thepattern formed in the seed layer 170. For example, the seed layer 170may include domains 162, 164 which define features, such as lines, whichhave very rough edges or non-uniformities in critical dimensions.Initially, certain chemical moieties or blocks of the supplementalcopolymers will align themselves with particular block domains 162, 164of the seed layer 170, which contain other chemical moieties whichinteract favorably with the blocks of the supplemental copolymers, e.g.,to encourage wetting of particular domains with particular blocks in thesupplemental copolymers. As the number of organized supplementalcopolymers grows and the heights of the organized supplemental copolymerdomains 182, 184 increase, however, the supplemental copolymers andprocess conditions may be selected such that interactions between thesupplemental copolymers dominate. Advantageously, because theinteractions between the blocks of the supplemental copolymers can berelatively homogeneous across the supplemental layer 180, the dominanceof the interactions between the blocks can cause the blocks toself-segregate and form domains 182, 184 which are more regular andbetter defined than the domains 162, 164 in the copolymer template.Thus, the domains 182, 184 in the supplemental layer 180 can havegreater uniformity in pitch and critical dimension than the domains 162,164 of the seed layer 170.

In addition, the supplemental copolymers can also advantageously levelout non-uniformities in thickness in the seed layer 170. For example, arelatively thick layer 180 of deposited supplemental copolymers may beless prone to form localized regions of different thicknesses than theseed layer 170, which can have thickness variations caused byinterfacial interactions with an underlying surface, or by depletion ofthe copolymers in the copolymer template before all block domains arefully formed. As a result, because the supplemental copolymers can formdomains up to a height proportional to the height of the supplementalcopolymer layer, the final mask formed by the supplemental copolymerscan advantageously have a more uniform thickness and, thus, greateruniformity in height]]

With reference to FIG. 12, the domains 184, 164 are selectively removed,leaving behind the domains 182, 162 and the guides 134. It will beappreciated that the domains 184, 164 can be removed in a single stepusing a single etch chemistry or can be removed using multiple etcheswith different etch chemistries. For example, where the domains 184, 164are both formed of PMMA and the domains 182, 162 are formed of PS, thedomains 184, 164 can be removed by performing a selective wet etch,e.g., using acetic acid as an etchant. In other embodiments, a dry oranisotropic etch may be appropriate where one of the domains can beetched at a faster rate than the other. It will be appreciated that thedimensions of the resulting features can vary, depending on the size ofthe copolymer used and process conditions. In some embodiments, theresulting pattern can advantageously comprise PS domains having acritical dimension of about 50 nm to about 2 nm, more preferably, about35 nm or less to about 3 nm, with a pitch of about 100 nm to about 4 nmand, more preferably, about 70 nm to about 6 nm. For example, the PSdomains can have a critical dimension of about 35 nm, with a pitch ofabout 70 nm. It will be appreciated that in other embodiments, thedomains 162 and/or the guides 134 can be removed instead, therebyleaving the domains 184, 164, with or without the guides 134.

With reference to FIG. 13, the domains 182, 162 and the guides 134 canbe used as a mask for processing of the underlying substrate 110. Forexample, as illustrated, the substrate 110 can be etched through themask using, e.g., an anisotropic etch that selectively etches thesubstrate relative to the domains 182 to transfer the pattern in themask to the substrate 110. In one example, where the substrate 110 isformed of silicon, it can be selectively etched relative to the blockdomains 182 using a fluorine-based dry etch chemistry, e.g., such asthat used to selectively remove silicon layers relative to photoresist.It will be appreciated that where the substrate 110 comprises layers ofdifferent materials, a succession of different chemistries, preferablydry-etch chemistries, can be used to successively etch through thesedifferent layers, if a single chemistry is not sufficient to etch allthe different materials.

It will also be appreciated that, depending upon the chemistry orchemistries used, the domains 182, 162 and the guides 134 may bepartially etched or worn during the transfer process. Advantageously,the domains 182 are sufficiently tall to allow etching or otherprocessing of the substrate 110 to be completed before the domains 182and/or 162 are completely etched away. Consequently, the tall domains182 can facilitate etching of more difficult to etch substrates.

With reference to FIG. 14, the mask overlying the substrate 110,including the domains 182, 162 and the guides 134, are stripped, leavingthe patterned substrate 110. With reference to FIGS. 15 and 16, thepattern formed in the substrate 110 can comprise, for example, lines(FIG. 15) or isolated pillar shapes, or conversely cylindrical holes(FIG. 16). The lines can form, e.g., interconnects for connectingelectrical devices, preferably devices arranged in an array, such as theelectrical devices which form memory cells in the array region of amemory device. In addition, the isolated pillar shapes can formelectrical devices, which are preferably disposed in an array, such ascapacitors for memory cells in a memory device. After the lines orisolated pillar shapes are formed, the partially fabricated integratedcircuit 100 is subjected to subsequent processing steps, includingforming ancillary electrical devices and electrical interconnects, toform a completed integrated circuit, e.g., a memory chip.

It will be appreciated that various modifications of the preferredembodiments are possible. For example, as noted above, the copolymerfilm 160 can be formed to a thickness below the height of the guides 134(FIG. 6). In addition, the guides 134 can also be formed to have aheight higher than the upper surface of the supplemental layer 180 (FIG.11). In some embodiments, this may be advantageous for increasingprocess latitude by eliminating the need to provide supplementalcopolymers which interact appropriately with the guides 134 to alignwith those guides 134.

Moreover, while discussed in the context of diblock copolymers, thecopolymers can be formed of two or more block species. In addition,while the block species of the illustrated embodiment are each formed ofa different monomer, the block species can share monomer(s). Forexample, the block species can be formed of different sets of monomers,some of which are the same, or can be formed of the same monomer, but ina different distribution in each block. Preferably, the different setsof monomers form blocks having different properties which can drive theself-organization of the copolymers.

In some embodiments, the hardmask and/or temporary layer overlying thesubstrate can be omitted. For example, the photodefinable material canbe formed of or replaced by a material which is compatible with thetemperatures and other conditions for copolymer self-organization and/orthe copolymer blocks may be used as a mask for etching the substratewhere an etch having sufficient selectivity for the substrate isavailable.

Also, while “processing” through a mask layer preferably involvesetching an underlying layer, processing through the mask layers caninvolve subjecting layers underlying the mask layers to anysemiconductor fabrication process. For example, processing can involveion implantation, diffusion doping, depositing, oxidizing (particularlywith use of a hard mask under the polymer mask), nitridizing, etc,through the mask layers and onto underlying layers. In addition, themask layers can be used as a stop or barrier for chemical mechanicalpolishing (CMP) or CMP can be performed on any of the layers to allowfor both planarization and etching of the underlying layers, asdiscussed in U.S. patent application Ser. No. 11/216,477, filed Aug. 31,2005, the entire disclosure of which is incorporated by referenceherein.

In addition, while illustrated applied to an exemplary sequence forfabricating integrated circuits, it will be appreciated that thepreferred embodiments can be applied in various other applications whenthe formation of patterns with very small features is desired. Forexample, the preferred embodiments can be applied to form gratings, diskdrives, storage media or templates or masks for other lithographytechniques, including X-ray or imprint lithography. For example, phaseshift photomasks can be formed by patterning a substrate which has afilm stack having phase shifting material coatings.

It will be appreciated from the description herein that the inventionincludes various aspects. For example, according to one aspect of theinvention, a method for forming a pattern over a semiconductor substrateis provided. The method comprises providing a template comprising apattern defined by domains formed of like blocks of a block copolymer. Alayer of self-organizing material is deposited on the template. Thepattern is transferred to the layer of self-organizing material.

According to another aspect of the invention, a method for forming amask pattern is provided. The method comprises depositing a layer ofblock copolymers. Blocks of the block copolymers are segregated to formdomains comprising blocks of the block copolymers. The domains aresubsequently vertically extended.

According to yet another aspect of the invention, method for forming amask pattern is provided. The method comprises providing a substratehaving an overlying block copolymer material disposed between guides forcopolymer alignment. A first substantially regular pattern of blockdomains is provided between the guides for copolymer alignment. Anadditional block copolymer material is deposited over the firstsubstantially regular pattern. A second substantially regular pattern ofblock domains is formed over the first substantially regular pattern.

According to another aspect of the invention, a partially fabricatedintegrated circuit is provided. The partially fabricated integratedcircuit comprises a first plurality of regularly spaced copolymer blockdomains overlying a substrate. A second plurality of regularly spacedcopolymer block domains is formed on the first plurality of copolymerblock domains.

In addition to the above disclosure, it will also be appreciated bythose skilled in the art that various omissions, additions andmodifications may be made to the methods and structures described abovewithout departing from the scope of the invention. All suchmodifications and changes are intended to fall within the scope of theinvention, as defined by the appended claims.

We claim:
 1. A method for forming a mask pattern, comprising: depositinga layer of block copolymers over a substrate; segregating blocks of theblock copolymers to form domains comprising like blocks of the blockcopolymers over the substrate; and subsequently vertically extending thedomains, wherein subsequently vertically extending begins on a levelabove and spaced-apart from the substrate.
 2. The method of claim 1,wherein vertically extending comprises: depositing a layer ofsupplemental block copolymers; and segregating and aligning like blockspecies of the supplemental block copolymers with some of the domains.3. The method of claim 2, wherein the supplemental block copolymers arethe same as the block copolymers, wherein aligning blocks comprisesmatching like blocks of the supplemental block copolymers with likeblocks of the block copolymers.
 4. The method of claim 2, whereinaligning blocks comprises performing an anneal.
 5. The method of claim1, further comprising forming a plurality of guides for copolymeralignment before depositing the layer.
 6. The method of claim 5, whereinthe guides are formed in a hard mask layer, wherein forming theplurality of guides comprises: forming a pattern in a photoresist layer;and transferring the photoresist pattern to the hard mask layer.
 7. Themethod of claim 6, wherein forming the plurality of guides furthercomprises trimming features formed in the hard mask layer aftertransferring the photoresist pattern.
 8. The method of claim 5, whereindepositing the layer comprises depositing block copolymers over andaround the plurality of guides for copolymer alignment.
 9. The method ofclaim 1, further comprising selectively removing domains andtransferring a pattern formed by the domains to an underlying substrateafter subsequently vertically extending the domains.
 10. The method ofclaim 9, wherein transferring the pattern forms electrical devices in anintegrated circuit.
 11. The method of claim 10, wherein transferring thepattern forms a photomask.
 12. The method of claim 1, wherein thedomains comprise vertical lamellae.
 13. The method of claim 1, whereinthe domains comprise vertically extending isolated pillars.
 14. Apatterning method, comprising: providing a repeating pattern of blockcopolymer domains over a substrate; providing a supplemental layer ofblock copolymers over the repeating pattern, the supplemental layerhaving a supplemental layer pattern substantially similar to therepeating pattern, wherein providing the supplemental layer of blockcopolymers is performed on a level above and spaced-apart from thesubstrate.
 15. The method of claim 14, wherein the supplemental layerpattern comprises domains disposed directly on like domains of therepeating pattern.
 16. The method of claim 15, further comprisingselectively removing some of the domains, thereby defining openingsextending from the supplemental layer to the substrate.
 17. The methodof claim 16, further comprising etching the substrate through theopenings.
 18. The method of claim 14, wherein the block copolymers ofthe repeating pattern comprise diblock copolymers.
 19. The method ofclaim 18, wherein the diblock copolymers comprise polystyrene.
 20. Themethod of claim 19, wherein the diblock copolymers further comprisepolymethylmethacrylate.